Field of the Invention
Embodiments of the present invention generally relate to distributed power systems and, more particularly, to a serially connected micro-inverter system having concertina output voltage control.
Description of the Related Art
Distributed power systems comprise a power source that generates direct current (DC) power, a power converter, and a controller. The power source may be a solar panel or solar panel array, a wind turbine or a wind turbine array, a hydroelectric generator, fuel cell, and the like. The power converter converts the DC power into alternating current (AC) power, which is coupled directly to the AC power grid. The controller ensures that the power conversion process operates as efficiently as possible.
One type of power converter is known as a micro-inverter. Micro-inverters typically convert DC power to AC power at the power source. Thus, each power source is coupled to a micro-inverter. A plurality of AC power outputs from the micro-inverters are coupled in parallel to the AC power grid. Since the outputs of each micro-inverter are coupled in parallel directly to the AC power grid, all the parallel connected micro-inverters are simply synchronized to the AC power grid.
Because of the parallel connected nature of a parallel connected micro-inverter system, the output voltages are substantial, e.g., hundreds of volts. Consequently, the inverters are typically buck-boost type inverters with an H-bridge output circuit that require a transformer to generate the high-voltage and switching transistors to handle the high-voltage within the H-bridge. The transformer and high-voltage transistors add significant cost to the manufacturing cost of a micro-inverter.
Therefore, there is a need in the art distributed power system that does not require transformers and high-voltage transistors.